A student armed with a shotgun apparently killed himself after opening fire at a Colorado high school, wounding two fellow students, police said Friday.

Arapahoe County Sheriff Grayson Robinson said the armed student entered the school and said he was looking for a specific teacher, calling him by name through the hallways. Robinson said another student confronted the gunman and then was shot.

"The teacher began to understand that he was being looked at [and] exited the school," Robinson said.

"The suspect has been found and has been deceased as a result of what appear to be a self-inflicted gunshot wound," he said.

The Associated Press quotes a hospital spokesman as saying the wounded student was taken into surgery. The other wounded student is also being hospitalized with a minor gunshot wound.

The AP says a third student was injured, but it was unclear if that student was shot.

The shooting took place at Arapahoe High School in Centennial, located about 8 miles from Columbine High School in Littleton, Colo., where 13 people were killed in 1999.

Update at 11:27 p.m. ET. Sheriff Identifies Alleged Shooter

Robinson said the student who opened fire was Karl Halverson Pierson, 18. He said the Pierson had had a "confrontation or disagreement" with the teacher he allegedly targeted.

He said teacher left the school after being alerted by other students in order to lure the shooter outside. "That was a very wise tactical decision," he said.

He said one victim underwent surgery and is in critical condition. Authorities are now saying that the second student taken to the hospital was covered in blood from the first victim and as not injured, as earlier reported.

Sheriff Robinson said that a 15-year-old girl who was severely wounded in the shooting remains in critical condition.

He said he thought the quick action of law enforcement helped save lives.

"The evacuation was done in an organized, thoughtful way," he said.

"I believe the shooter took his own life because he realized he was about to be engaged" by law enforcement, Robinson said.

He said authorities know the identity of the suspect but were not at liberty to release a name.

Two Molotov cocktail-type devices were found at the scene, the sheriff said.

Update at 5:15 p.m. ET. Shooter Thought To Have Acted Alone:

In a second news conference, Robinson said the shooter appeared to be acting alone. He said initially authorities believed there had been a confrontation between the shooter and the student who was most seriously wounded, but it could be that the injured student was simply "in the way."

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Transcript

AUDIE CORNISH, HOST:

From NPR News this is ALL THINGS CONSIDERED. I'm Audie Cornish.

MELISSA BLOCK, HOST:

And I'm Melissa Block. This afternoon a student opened fire at Arapahoe High School in Centennial, Colorado, near Denver. Arapahoe County Sheriff Grayson Robinson spoke to reporters later in the day. He said the student was armed with a shotgun.

SHERIFF GRAYSON ROBINSON: Today at 12:33 p.m. a lone gunman entered the school on the west side. The gunman came into the school and immediately asked for the location of a very specific teacher and he named that teacher by name.

BLOCK: The sheriff says one student, a 15-year-old girl, was shot and is in critical condition. Another was shot and sustained a minor injury and has now been released from the hospital. Sheriff Robinson says the suspect has died of an apparent self-inflicted gunshot wound.

Joining us from Centennial is Colorado Public Radio Megan Verlee. And Megan, what more can you tell us about what happened today?

MEGAN VERLEE, BYLINE: Well, as it's been described, the student walked into the school openly carrying that shotgun and asking for that teacher. As soon as students heard that they went to warn the teacher. He got out of the school very quickly. And Sheriff Robinson described what happened.

ROBINSON: He departed the school. That was a very wise, tactical decision. He took himself away from the school with an effort to try and encourage the shooter to go with him.

VERLEE: Now apparently that effort was not successful; the shooter stayed in the school. And when armed deputies got to him about five minutes later, he had killed himself.

BLOCK: Megan, any more information about this student who carried out the shooting, what his motives may have been, or any connection to this teacher who he was specifically targeting?

VERLEE: The sheriff that have ID'd the student but are not releasing anything much about him. He did say that this was an act of, quote, "revenge" for some sort of confrontation or altercation between him and the teacher.

BLOCK: Megan, we mentioned that the one student who was not badly injured has been treated and released, but there is the other 15-year-old girl in critical condition. Any other word on her status?

VERLEE: Just this is very serious. She was taken immediately into emergency surgery. Apparently, she was just a bystander to this, had not confronted the gunman, but was very much in the wrong place.

BLOCK: There were horrifying images coming out of the school of these high school students filing out with their hands over their heads, being frisked by police. And you went to the church where parents were then being reunited with their children. It must have been just a wrenching thing to see.

VERLEE: It really was. As often happens now with these disasters and emergencies, so many of those parents were on cellphones even before their students got there, checking in with them, trying to get word. But that didn't really ease the tension until the kids started arriving on buses and running out to their parents. You got a sense of how quickly they had to leave the school. There were kids in gym shorts and t-shirts. Nobody had a backpack. It was cold today and these kids came off the bus looking like they had just come out of gym class.

BLOCK: This high school, Arapahoe High School, is not far from Columbine High School. Of course, we all know about the mass shooting that took place at the school there in 1999. And there were protocols established after that shooting for how to deal with situations like this. Protocols that officials there today said had become all too familiar. They've had to do this too many times.

VERLEE: Oh yes. The one big thing they learned from Columbine is that you go in fast. At Columbine, they waited and more students died. Today, as soon as law enforcement knew what was going on, they were running and rushing into that school.

BLOCK: And again, repeating the news. We've talking about a shooting today at Arapahoe High School. Again, the gunman is dead of an apparent self-inflicted gunshot wound. One other student, a 15-year-old girl, is critically wounded, and a third has been treated and released. Transcript provided by NPR, Copyright NPR.